This is a continuation-in-part of commonly assigned co-pending U.S. patent Ser. No. 08/435,709, entitled "Cellular Private Branch Exchange," filed May 4, 1995, now U.S. Pat. No. 5,734,699.
The following co-pending U.S. patent applications are incorporated herein by reference for all purposes:
"Cellular Private Branch Exchange," filed May 4, 1995, U.S. Pat. No. 5,734,699.
"Cellular Communication Network Having Intelligent Switching Nodes," filed May 4, 1995, U.S. Ser. No. 08/435,838, now U.S. Pat. No. 5,577,029.
"Configuration-Independent Methods And Apparatus For Software Communication In A Cellular Network," filed on even date, U.S. Ser. No. 08/730,652, Attorney's Docket No. WAVEP005 and the earlier filed provisional application entitled "Configuration-Independent Methods And Apparatus For Software Communication In A Cellular Network" filed Nov. 10, 1995 Application No. 60/006,455 by inventors Priscilla Marilyn Lu and Timothy Richard White from which that application claims priority under 35 U.S.C. 119(e).
"Spread Spectrum Communication Network Signal Processor," filed on May 4, 1995, Ser. No. 08/434,554, now U.S. Pat. No. 5,682,403.
"Cellular Base Station With Intelligent Call Routing," filed on May 4, 1995, Ser. No. 08/434,598, now U.S. Pat. No. 5,734,979.
"Spread Spectrum Communication Network With Adaptive Frequency Agility," filed on May 4, 1995, Ser. No. 08/434,597, now U.S. Pat. No. 5,781,582.
For ease of reference, a glossary of terms and abbreviations is provided herewith as Appendix A.
The present invention relates generally to cellular communications networks. More particularly, a private cellular exchange network that has the ability to optionally act as a base station subsystem in an even larger network to permit nonnative handsets to use the local network's resources is described.
Presently, there are a variety of wired and wireless private branch exchanges (PBX's) that are commercially available. By way of example, FIG. 1 diagrammatically illustrates a conventional wireless private branch exchange system (wPBX) 100. As seen therein, the wPBX 100 is coupled to one or more external lines 102, which typically couple the wPBX to a public network. The wPBX 100 is arranged to control a plurality of base units 108 and is coupled to the base units by fixed wiring 104. It should be appreciated that the wPBX may control any number of base units, although for simplicity of illustration, only one such base units is explicitly shown. Each base unit 108 includes an antenna 110 to facilitate cordless communication between the base unit and one or more associated cordless handsets 112. In the typical wireless PBX system, each base unit 108 controls a pair of cordless handsets.
Although the described wPBX system offers the advantages associated with cordless handsets, there are several significant limitations. To begin with, in wireless PBX systems, the telephone number is associated with a given frequency, which is in turn associated with a fixed port on the PBX. Therefore, from the point of view of the PBX, the cordless handset is "fixed" to a PBX port just as in normal wired PBX's. Because of this, even when the wPBX is interconnected in a wPBX network, a cordless handset cannot be taken to another location controlled by another wPBX unit and still able to make and receive calls associated with its assigned phone number without having to undergo administrative moves and changes, e.g. reprogramming the wPBX itself. Consequently, the range of each cordless handset is limited by the range of the base unit with which it is specifically associated.
Further, neither the cordless handsets nor the prior art wireless PBX's have any roaming or hand-off capabilities. To illustrate, consider the situation when cordless handset 112 travels (i.e. roams) out of the range of base unit 108 during use into an area controlled by another wireless PBX. In such an event, the communications data stream is nevertheless cut off. Thus, from the perspective of wPBX 100 or the public network to which link 102 is coupled, the fact that cordless handsets 112 and 114 communicate with base 108 in a cordless manner is irrelevant. Since there are no roaming and no hand-off capabilities between base units or wPBXs, the manner in which cordless handsets 112 are coupled to base unit 108 does not provide the user with any additional advantages besides the fact that cordless handsets 112 and 114 may be made cordless inside the range defined by the transceiver within base unit 108.
Another disadvantage of typical wireless PBX systems involves their use of low-power and proprietary transceivers, which significantly limit the range over which a cordless handset can be taken from its associated base unit. By way of example, the radius of operation of the cordless handsets is typically limited to around 200 meters. Further, when calls are made among cordless handsets of the same wPBX, the call paths are typically switched, or cross-connected, at the wPBX level. In other words, the actual switching is centralized at the wPBX even if cordless handsets of the same base unit desire to communicate among themselves, e.g., between cordless handsets 112 and 114. This is because the switching function can not be delegated from wPBX unit 100 down to subsystems below it in the hierarchy, e.g., to base 108. When calls are always switched at the highest level of the hierarchy, call paths to and from the cordless handsets are oftentimes unnecessarily back hauled all the way to the highest level, i.e., the wPBX, although it may be more efficient to cross connect closer to the cordless handsets, i.e. at a base unit at a lower level of the hierarchy.
Another disadvantage of the prior art wireless PBX's relates to its inablility to authenticate calling and destination handsets to ascertain whether the handsets currently in communication with the system is in fact the intended ones. This is because any prior wireless handset that happens to be on the same frequency and utilizes the same protocol as the base unit can intercept a given call. Because of this limitation, there is no way in the prior art wPBX to define and discriminate among the particular handsets that are authorized to use the resources of the wireless system to make and receive calls from those that merely have the technical ability, but not authorized, to use those resources. For the purpose of the present disclosure, the former is regarded as native handsets and the latter nonnative ones.
It should be appreciated that in some applications, it would be desirable to provide a system which discriminates between native and nonnative handsets and permits nonnative handsets that enter an area controlled by a private exchange system to utilize the resources of that private exchange system to seamlessly connect to a public network.